Keep out - for the next 250,000 years

NUCLEAR waste has to be kept isolated from humanity for at least a quarter of a million years, which is more than 20 times longer than the entire history of civilisation, from the time the first plough was put to the ground. No political problem facing government has quite such long-term implications.

For 40 years, the policy of successive British governments has been, in a classic Whitehall phrase, to "dispose of radioactive wastes at appropriate times and in appropriate places". In plain English, this has meant trying to put it in a hole and forget about it.

Now, in an unprecedented change of policy, ministers are quietly preparing to abandon plans to dump dangerous nuclear waste in Britain. This threatens the future of the controversial Sellafield nuclear complex, and is likely to presage the scrapping of Nirex, the nuclear industry's much-criticised waste disposal firm.

The move follows a disastrous series of botched attempts by Nirex to find a dump site, and amounts to a tacit admission that no one knows how to dispose of the waste safely, more than 20 years after a Royal Commission concluded that it would be "irresponsible and morally wrong" to expand nuclear power until a solution was found.

The impending decision, to store - and closely monitor - intermediate level nuclear waste, instead of dumping it, will mark an abrupt conversion to the environmentalist side of the debate. Pressure groups, such as Greenpeace and Friends of the Earth, have long argued that the industry does not know enough to find a safe enough hole for the wastes, and may never be able to do so. They say the "least worst option" is to put them in special, closely watched stores, at existing nuclear sites like Sellafield - from which they can be retrieved if something goes wrong.

BOTH SIDES have claimed the moral high ground in what has been a finely balanced argument. The industry and its allies say it is irresponsible to leave the waste for future generations to look after. The greens retort that it is better to pass on an unsolved problem than an irrevocably contaminated environment.

Now, top civil servants have told a House of Lords committee, in so far unpublished evidence, that "the Government considers it important that the design of any repository should allow for the monitoring of the waste after its emplacement, and that it should turn out to be retrievable if this proves to be necessary". In other words, "disposal" - a polite word for dumping - is no longer "appropriate".

Britain has about 70,000 cubic metres of intermediate-level wastes, and about 700 cubic metres of the most dangerous high level ones (low level waste is already put in a shallow dump at Drigg, near Sellafield). The amounts will rise to 220,000 cubic metres and 1,600 cubic metres by the time the present nuclear reactors have come to the end of their working lives.

The requirement that both types must remain isolated from humanity for at least a quarter of a million years is a geological not a human timescale and it poses vast problems. In 250,000 years, ice-ages will come and go, seas rise and fall, land sink and emerge from seas. Tectonic plates will move, and continents continue their drift. Scientists have recommended that waste would have to be buried at least 1,000 feet down to allow for possible erosion of the soil and rock above it.

Finding a spot for a dump that will be immune from all these processes seems mindboggling enough. Adding in the human factor makes it even worse. Civilisations will surely collapse, be born, and fall again during that period; there is certainly no guarantee that all our descendants will be even as technically advanced as we are.

For decades, the nuclear industry, and its followers in Whitehall and Westminster, had a simple answer to these questions: Micawaberism. Something, they believed, would turn up. In 1976 - 30 years after the start of Britain's nuclear industry, 20 after its first nuclear power station started feeding electricity into the grid - an investigation by the Royal Commission on Environmental Pollution uncovered astonishing complacency.

The Royal Commission - chaired by Lord Flowers, himself then a member of the UK Atomic Energy Authority - found that neither his body nor British Nuclear Fuels Ltd (BNFL) had given "any indication that they regarded the search for a means of final disposal of highly active waste as at all pressing". And it added that it had been "unable to discover any clearly formulated policy" for the disposal of intermediate-level waste.

It recommended: "There should be no commitment to a large programme of nuclear fission power until it has been demonstated beyond reasonable doubt that a method exists to ensure the safe containment of long-lived, highly-radioactive waste for the indefinite future." Any other course would be "irresponsible and morally wrong". Even then, the industry took the issue lightly. "The lion of nuclear fission has been tamed," boasted one BNFL chief. "It remains to clear up what he leaves in his cage."

Crazy sci-fi ideas were advanced. The waste could be fired into space, or into the sun, it was suggested - until someone pointed out the appalling consequences if just one rocket failed. Similar fears of the effects of an accident scuppered proposals to insert it beneath the Earth's crust, between the edges of tectonic plates. Another idea was to place the waste on the Antarctic ice-sheet, so that its heat melted the ice beneath it until it eventually worked its way down to the bedrock: this, fortunately, was outlawed by international treaty. Another treaty banned disposal at sea, after a long campaign by environmentalists (aided by John Prescott, swimming down the Thames in protest).

The options narrowed to the two current ones - dumping the waste in holes in the ground, or storing it. But attempts to find disposal sites in Britain have been a farcical chronicle of failure. First, early in the Thatcher years, ministers abandoned plans to dump high-level waste in Scotland. Then, proposals for disposing of intermediate-level waste in an anhydrite mine on Teeside were abandoned after public protests. On the eve of the 1987 general election, Nicholas Ridley (then environment secretary) pulled the plug on a shortlist of four sites - all in Tory constituencies.

Nirex staked its last throw on a site near Sellafield. It did so on political, rather than scientific, grounds; there was less chance of protests as the nuclear industry is the biggest local employer. But reports by the Government's pollution inspectors - which Nirex tried to suppress but were published in the Independent on Sunday - showed radioactivity would rise to the surface from the planned dump.

On the day last year's general election was called, the then environment secretary, John Gummer, defied opposition from deputy prime minister Michael Heseltine and refused to give Nirex the go ahead even to construct an underground laboratory on the site. This and the coming change of policy now pose a massive problem for the industry, and for Sellafield. They undermine the already shaky rationale for the reprocessing plant, which separates used nuclear fuel into plutonium, uranium and nuclear waste. The plutonium and uranium are no longer needed to fuel reactors and if the waste is to be stored, environmentalists argue, it might as well be stored in the unreprocessed spent fuel rods.

It also vastly complicates the arrangements under which the complex's controversial Thorp plant reprocesses used fuel from Germany and Japan. The process produces vast amount of intermediate waste. The Government's policy is to return this, but it had planned to save transport costs by sending back smaller amounts of high-level waste of the same radioactivity. But that depended on having a dump for intermediate-level waste.

So Sellafield will now have to send it all back, increasing cost, and probably invoking furious protests at the shipments in Japan and Germany. Only last week, a shipment carrying 24 tons of nuclear waste was prevented from entering a Japanese port for several days, while, last year, protests against the transport of waste in Germany necessitated the biggest mobilisation of troops since the Second World War. If they have to take back so much waste, Germany and Japan may be reluctant to send fuel for reprocessing, and the already fragile economics of the plant will be devastated.

NIREX could be another casualty. Ministers are thinking of scrapping it. They believe the industry should fund any new body, but are likely to insist that it is less secretive and more accountable to Parliament and public.

The Government has not given up the idea of burying waste underground if it is stored not dumped, is monitored and can be retrieved. Eventually, it believes, underground disposal will be the only long-term solution. If it pursues this, it is likely to have difficulty finding a site. "We will stop any plans for an underground repository," says Dr Patrick Green, senior nuclear campaigner for Friends of the Earth. "There is not a community in the country that would accept it."